Power-stoked coal-fired heating unit



p 1964 J. L. MARGETTS 3,l49,625

POWER-STOKED COAL-FIRED HEATING UNIT Filed Oct. 4, 1961 2 sheets sheet l .ea-,a /7-/ INVENTOR.

JOHN L. MARGETTS ATTORNEYS p 22, 1954 .x. L! MARGE'n-s &149.625

POWER-STOKED COAL-FIRED HEATING mm' Filed Oct. 4, 1961 2 Sheets-Sheet 2 ATTORNEYS United States Patent O 3,149,625 POWER-STOKED CUAL- FRED HEATENG UNT John L. Margetts, 2182 lerhley Ave., Salt Lake City, Utah Filed Get. 4, 1361, Ser No. 142,827 8 Clairns. (Ci. 126-110) This invention relates to hot air heaters and furnaces having built-in coal stokers, and is concerned with providing an improved Construction for same whereby greater heating efliciency is attained.

In accordance with the invention, a box-like, externallyfinned, heat exchanger provides primary heating surfaces and defines, internally a combustion chamber and an up- Ward continuation thereof servng as a heat-extraction chamber. An air jet pipe extends downwardly through the interior of the heat exchanger to a termination within the combustion chamber directly above the stoker-fed firebowl, so that, while supplying secondary air for improved combustion, the air jet will deect the flames laterally against the walls of the cornbustion chamber, where the hot gases will rise in close heat-imparting relationship with the upper walls of the heat exchanger.

A feature of the invention is a forced air supply branching from a single blower to communication With the firebowl and with the air jet pipe, and individually controlled dampers in the respective branches so that supply of both underfeed and overfeed air may be closely controlled relative to each other.

Other features are the use of the pressure air to prevent backsmoking, the provision of a handy ash receptacle in an air-circulation chamber between heat exchanger and heater housing, and the provision of a special lining for the combustion chamber.

A specific embodiment of apparatus representing what is presently regarded as the best mode of carrying out the invention is illustrated in the acconpanying drawings.

In the drawings:

FIG. 1 is a perspective View of a heater adapted for installation within the living quarters of a home;

FIG. 2, a horizontal section taken on the line 2--2 of FIG. 1 and considerably enlarged;

FIG. 3, a vertical section taken along the jogged line 3-3 of FlG. 2 and drawn to the same scale;

FIG. 4, a fragmentary portion of FIG. 4, illustrating one aspect of the particular Construction during operation; and

FIG. 5, a fragmentary Vertical section taken on the line 5-5 of FIG. 2.

Referring to the drawings:

In the form illustrated, a box-like heat exchanger 19, FIG. 3, is fabricated from some suitable material, such as aluninized sheet steel, to provide a combustion chamber 11 and an upward extension 12 thereof serving as a heat-extraction chamber. A hollow, substantially air-fight base 13 is advantageously formed by integrally extending the sheet steel below a refractory bottom 14 which mounts a firebowl 15.

The heat exchanger is externally finned, as by stitch seam welding channel members 16 entirely around the periphery thereof at closely spaced intervals along its height. The lines of Welding are indicated at 16-1 in FIG. 3.

A sheet metal housing 17 surrounds heat exchanger 19 and its base 13 in spaced relationshp therewith to form an air-circulation chamber 13, which is supplied with air by ventilating fan 19, FIG, 2. The housing is ported and covered With louvres or grillwork at 20 and 20-1, FIG. 1, to permit outflow of heated air, and is provided with a down-swinging door 21 giving access to a side-swinging fire door 21-1, FIG. 2, in the heat exchanger, so that clinker can be removed. A tunnel structure 17-1 forms a substantially air-tight entryway from the outer door to the inner door, and an ash bucket 22, FIG. 5, within such entryway and below inner door 21-1 is available to receive the hot clinker.

A hopper 23 for coal is formed against one of the side walls of housing 17, preferably by partitioning a sideward addition 24 to such housing 17, thereby providing enclosed space for mounting a forced air blower 25 and its motor 26, FIG. 2. A hinged cover 27, FIGS. 1 and 3, gives access to the hopper.

Stoker mechanism is provided in conjunction With hopper 23, including coal feeding means in the form of a feed screw 23, FIGS. 2 and 3, Operating in a tube 29 which leads from the bottom of the hopper into firebowl 15 by way of the interior of base 13. The Stoker mechanism is driven by motor 26 through a conventional gear box 26-1 to which it is connected by a V-belt drive 26-2.

Blower 25 has two air delivery conduits 30 and 31 leading therefrom. An air jet conduit 32 extends upwardly through hopper 23 from a connection With blower conduit Stl and passes horizontally through the upper air circulation passage 18 to the center aXis of heat cxchanger 10, Where it turns and extends downwardly through the closed top wa of such heat exchanger to termination in a jet orifice 33 directly above the center of firebowl 15. The upwardly extending portion 3241 of such conduit 32 is advantageously formed by a sheet metal pipe of rectangular cross-section, FIG. 2, While the remainder is preferably black iron pipe, as indicated.

The interior of hopper 23 is desirably pressurized by the provision of a vent 34 near the upper end of portion 3241. of air jet conduit 32 to prevent back-smoking.

lower conduit 31 discharges into the interior of base 13, where the air passes into firebowl 15 through passages 35. It is also desirable that coal feed tube 29 be ported, as at 36, to pressurize against any tendency for backsmoking into hopper 23.

Relative flow of overfeed air through air jet conduit 32 and of underfeed air into and through base 13 is regulated by dampers 37 and 38, FIG. 3, which are preferably placed in blower conduits 30 and 31, respectively, and are individually controlled, as by means of manually operated handles, respectively, see 39, FIG. 2.

The jet of air directed downwardly on the burning coal in firebowl 15 from jet orifice 33 diverts the flames 40, FIG. 4, outwardly against the sidewalls of heat exchanger 10 within the combustion chamber 11, while at the same time, and because of the intense turbulence, eifectively shortening such flames to prevent or limit soot formation. Moreover, while providing better combustion to increase available heat, the jet air prevents the formation of coke trees at the center of the firebowl burner.

In order to better withstand high flame temperature, a lining 41 is provided for the combustion chamber 11 in the form of heat resisting sheet material secured in face to face relationship With the interior walls of such chamber. Stainless steel is preferably utilized for the lining, since it is highly heat resistant and has a different coeicient of thermal expansion than has the aluminized steel walls of the heat exchanger. This means that the lining will tend to buckle inwardly, somewhat as indicated at 42 in FIG. 4, under intense flame heat, thereby limiting the heat passed to the less resistant hoat exchanger walls within this combustion zone.

For more effective heat transfer and to limit buckling of lining 41 inwardly of the combustion chamber, it is preferred to secure both the fin members and the lining to the walls of the heat exchanger along stitch seam Welds in common.

Combustion gases pass to the atmosphere through a stack 43 in customary manner.

Whereas the invention is here specifically illustrated and described with respect to what is presently regarded as the best mode of carrying it out in actual practice, it should be understood that various changes may be made without departing from the inventive concepts particularly pointed out and distinctly claimed herebelow.

I claim:

1. In a power-stoked, coal-fired, heating unit including in combination a box-like heat exchanger having Walls providing primary heating surfaces and dening, interiorly, a cornbustion chamber and an Upward extension thereof serving as a heat extraction chamber; a fire-'bowl disposed substantially centrally in the bottom portion of said combustion chamber; a stack for the discharge of combustion gases; a supporting base for the heat eX-. Changer; a ported, air-circulation housing enclosing the heat exchanger; means for feeding coal into said firebowl; blower means including Conduit means for delivering an air jet downwardly toward and onto combustion taking place in said fire-bowl; damper means for controlling delivery of air through said Conduit means; means for driving the stoker and the blower; fins of steel having portions Secured in close face-to-face relationship with the exterior faces of said heat exchanger wall; and heat-` resisting, sheet steel lining said combustion chamber and Secured in close face-to-face relationship with the interior faces of said heat exchanger wall, said fins and lining being Secured along lines of intermittent welds in common.

2. A coal-fired heating unit, comprising walls defining a combustion chamber, including lateral walls of sheet steel subject to thermal expansion; a lining secured to said lateral walls in face-to-face relationship therewith internally of said chamber, said lining being of heatresistant sheet steel subject to thermal expansion; a series of relatively closely spaced lines of intermittent welding securing said lining to said lateral walls; means for firing coal into said combustion chamber upwardly from the bottom thereof; a series of relatively closely spaced fins of steel Secured to said lateral walls in face-to-face relationship therewith externally of the combustion chamber, said fins being secured to said lateral Walls by the same lines of ntermittent welding which secure the lining to said lateral walls; a casing surrounding the lateral Walls of said cornbustion chamber in spaced relationship thereto; and, means for circulatirg a fluid to be treated through said casing in hoat exchange relationship with said fins.

3. A coal-fired heating unit, comprising walls defining a ccmbustion chamber, including lateral walls of sheet steel subject to thermal expansion; a lining Secured by means of a series of relatively ciosely spaced lines of in termittent welding to said Walls in face-to-face relationship therewith internally of said chamber, said lining being of heat-resistant sheet steel subject to thermal expansion and having a different coefiicient of thermal expansion than the sheet steel which provides the walls of the heat exchanger, the said lines of intermittent welding being spaced apart sufiiciently to provide spacing between said lining and walls upon relative expansion thereof; and means for firing coal into said combustion chamber.

4. The improvement of claim 1, wherein the sheet steel lining the combustion chamber in face-to-face relationship with the interior faces of the heat exchanger walls has a different coeicient of thermal expansion than the sheet steel which provides the walls of the heat ex- Changer.

S. The improvement of claim 4, wherein the steel providing the walls of the heat exchanger is aluminized sheet. e

6. The improvement of claim 5, wherein the sheet steel lining the combustion chamber is stainless steel sheet.

7. The coal-firedheating unit of claim 3, wherein the steel providing the walls of the heat exchanger is aluminized sheet.

8. The coal-fired heating unit of claim 7, wherein the sheet steel lining the combustion chamber is stainless steel sheet.

References Cited in the file of this patent V UNITED STATES PATENTS 

3. A COAL-FIRED HEATING UNIT, COMPRISING WALLS DEFINING A COMBUSTION CHAMBER, INCLUDING LATERAL WALLS OF SHEET STEEL SUBJECT TO THERMAL EXPANSION; A LINING SECURED BY MEANS OF A SERIES OF RELATIVELY CLOSELY SPACED LINES OF INTERMITTENT WELDING TO SAID WALLS IN FACE-TO-FACE RELATIONSHIP THEREWITH INTERNALLY OF SAID CHAMBER, SAID LINING BEING OF HEAT-RESISTANT SHEET STEEL SUBJECT TO THERMAL EXPANSION AND HAVING A DIFFERENT COEFFICIENT OF THERMAL EXPANSION THAN THE SHEET STEEL WHICH PROVIDES THE WALLS OF THE HEAT EXCHANGER, THE SAID LINES OF INTERMITTENT WELDING BEING SPACED APART SUFFICIENTLY TO PROVIDE SPACING BETWEEN SAID LINING AND WALLS UPON RELATIVE EXPANSION THEREOF; AND MEANS FOR FIRING COAL INTO SAID COMBUSTION CHAMBER. 